Hi! I'm currently running QB for Mac Desktop 2015 on a Macbook Air and an iMac (I keep my QB file on Google Drive and am careful to only access it from one at a time). Both of those computers are still running old OS systems (Yosemite on the Air and I'm not positive which on the desktop, but definitely not the most current version) and I remember some had trouble with updating QB2015 when Sierra came out, which was why we've never done that yet, or installed the last update to QB.

I've just purchased the 2019 QB Desktop for Mac after a very traumatic attempt to switch to the online option over the summer, and I want to make sure I am not going to mess everything up again, so am hoping for some hand holding and advice please.

First, I have a good number of imported online banking transactions that are not classified and transferred out of the "holding" area yet. Do those need to be done before any kind of upgrade/transfer to the new version or even just the OS upgrade? I am terribly behind on our bookkeeping and want to be sure I don't do things in the wrong order and make even more work for myself when there's already so much.

What's the ideal order for doing all of these updates? Do I update QB to R15 first and then the computer(s) to High Sierra or the other way around? What needs to be done if anything to my QB file before installing the new 2019 version? 

Finally, will I still be able to run the 2019 program on two computers (not simultaneously) as I have been in the past?

Thanks in advance for your help!